The present invention relates to electromechanical machinery, and more particularly, to such machinery utilizing a disc-type rotor.
Electrical rotating machines, such as motors or generators, utilizing disc-type rotors are well known in the art. Such machines utilizing wires conventionally wound in laminated or shingle-lapped fashion on the disc rotors are frequently unsatisfactory in that the rotors are undesirably bulky and irregular winding arrangements are required. Arrangement of the wires conventionally into a suitable winding pattern usually takes the form of a crossover of wires thereby resulting in a large air gap between stators and a consequential reduction in flux in the gap.
To overcome the aforementioned disadvantages, printed circuit-type machines have been used in which a conductive pattern is etched or printed on the faces of a thin disc of insulating material to form the armature. An example of a printed disc armature is disclosed in my earlier U.S. Pat. No. 3,096,455 issued on July 2, 1963. This type of motor provides a number of advantages. For example, these machines exhibit virtually no magnetic flux distortion and eddy current induction. The printed circuit armature machines are further advantageous in that they may include a large number of poles without increasing eddy loss and while increasing the back e.m.f. These machines, however, suffer from the disadvantage that, when fabricating a high power machine, the necessary increase in thickness of copper winding is difficult to accomplish with etching techniques. Furthermore, the limitations of etching techniques are such that the minimum obtainable separation between turns in the winding are of the order of twenty to thirty thousandths of an inch. This limits the number of turns of wire which can be provided in a given area. In addition, etching techniques require thin metal conductors, and this increases the resistance of the armature winding. The combination of relatively few turns in a given area combined with relatively high armature resistance results, of course, in a relatively low power machine.
Some disc-type machines employ a single layer of conductor winding to form the armature between a stator and a magnetic closure plate, such as shown in British Pat. No. 1,299,057 issued on Dec. 6, 1972, to Kolimorgen Corporation. Such machines are usually characterized by relatively low power and efficiency. U.S. Pat. No. 2,847,589 issued on Aug. 12, 1958, to A. W. Haydon shows another version of a disc-type machine wherein the coils are wound in flat spirals on both sides of an insulated disc. This type of arrangement produces a relatively low power machine due to the small number of coil turns per stator pole and the low density of copper winding per gap thickness. Other known arrangements can boost the efficiency of small disc-type machines to as high as 75 to 80% by using high-strength alnico or rare earth magnets, but these types of magnets are very costly and increasingly scarce due to shortages in the supply of the constituent elements. High efficiencies of up to 90% have been achieved in larger, high-power lamination-type motors, but these motors are typically of the order of several hundred pounds and deliver relatively low power in proportion to their weight.